Cannot install dovecot with the urpmi command

First of all, thank you very much for this helpful site. I just want to say that I am new to the linux system and I am currently trying to install a Mandriva Spring Free 2008.1 server following the guide here http://www.howtoforge.com/perfect-server-mandriva-2008.1-p5, however, I am getting the following message when trying to install dovecot:

[root@mydserver var]# urpmi dovecot
> No package named dovecot

I don't know how to proceed from here. Can somebody point me to the right direction. I'm sure there must be another way to install dovecot.